Calender rolls which are heated by a liquid medium, i.e. a circulated heating fluid, are commonly used in the paper, rubber and synthetic resin (plastics) industry and can have a considerable length. Such rolls must be manufactured and operated within narrow tolerances, especially with respect to their journaling members or stub shafts and can have temperatures well above ambient temperatures, e.g. as much as 200.degree. C.
The stub shafts could not effectively be provided heretofore with axial bores through which the heating medium was conducted to the bores or passages of the roll without problems.
For example, when the array of peripheral passages was connected by individual bores with a throughgoing passage of the journaling shaft, various flow velocities of the medium through these connecting passages, variations in the wall thickness of the latter connecting passages, the thermal inertial of the surrounding regions of the roll and like factors resulted in variations in the heating effects at various locations, making it expensive to fabricate calender rolls operating within high tolerances or narrow tolerances, and to maintain such calender rolls.
To reduce these costs and to provide the heating medium so that it only heated the regions of interest, calender rolls were developed which had a hollow interior and were connected at one end with appropriate fittings for feeding the medium to and removing the medium from the hollow calender roll. Within the calender roll the medium was distributed by baffle bodies or other displacement-causing elements forming an annular passage cross section for the medium which was of comparatively small thickness. This provided a better defined path for the medium and in large measure avoided the problems which hitherto arose with thermal inertia. However, with these calender rolls another problem developed, namely, a problem with respect to acceleration and velocity of the calender roll. As the calender roll accelerated or was rotated at high speed, for example, the baffle arrangements within the hollow calender roll tended to loosen or become liberated, creating significant problems of maintenance and down time.
Since such calender rolls must be accelerated frequently from standstill at high rates to maximum speed, e.g. in the paper, foil or strip forming field, the shocks which were applied to the calender roll as a result of the problems of securing the displacement or baffle bodies caused tearing, deformation and like damage to the product as well.
Not only was repair of the roll costly and time consuming, but significant danger of product damage arose.